This invention concerns an ice or snow particle generator, also called nucleation device or nucleator, integrated in a pressurised water spray head for the production of artificial snow.
These nucleation devices are practically compulsory when artificial snow is generated using simple water spray heads for rapid seeding and production of snow, i.e. even under limit temperature and humidity conditions.
The nucleation devices or nucleators are devices particularly sensitive to atmospheric conditions and especially to frost.
These nucleators operate moreover with very small water flowrate and are generally supplied by a special system that adjusts the flowrate and the pressure, whereas the said system is branched from the pressurised water supply system to the various nozzles of the spray head.
This invention suggests a nucleation device that, by its design and its association with the spray head, enables to overcome the shortcomings mentioned above.
It enables to overcome the shortcomings due to atmospheric conditions, such as frost, that clog the flow orifices because of the relatively small cross sections through which pressurised water flows.
It also enables to do away with complicated installations, while simplifying to a vast extent, the means that enable to feed these nucleation devices.
The nucleation device according to the invention comprises means for injecting a small pressurised water jet into an air stream, at high speed, with a very high air/water ratio, and the air-water mixture takes place either internally in a mixing chamber integrated in the spray head or externally, i.e. outside the said head, and whereas these water injection means at least are situated in the said head and are partially immersed in the water system under pressure that supplies the spray nozzle(s) permanently and, simultaneously, the said injection means.
Still according to the invention, the air/water ratio of this nucleation device is at least equal to 200 and the injection of water into the pressurised air stream takes place through one or several orifices of very small cross section, whose diameter is approx. 1 mm or smaller. This particularly small cross section enables to carry out high load loss at the nucleator and especially avoid resorting to any pressure relief system when the pressurised water comes from the supply system of the spray head nozzles. The pressure in this supply system of the nozzles may vary in large proportions, without influencing the operation of the nucleation device.
Still according to the invention, the nucleation device that performs external mixing comprises an air spray nozzle that is fitted with a baffle in order to produce a flat spectrum jet, and it contains a nozzle or tip for water spraying, whose jet strikes the flat air flow with an angle of approx. 45xc2x0.
According to an embodiment variation, the nucleation device is in the form of a high-pressure mini snowmaker supplied with compressed air and directly with pressurised water via the supply duct of the spray nozzle(s), whereas the said mini snowmaker is in the form of a cartridge located in the spray head and this cartridge extends between a pressurised air supply duct and the downstream external wall of the said head, while going through at least one pressurised water supply duct to one or several spray nozzles.
Still according to the invention, the mixing chamber of the mini snowmaker is cylindrical in shape and its diameter is slightly greater than the diameter of the end nozzle or tip, which nozzle has an outlet orifice whose section, that is circular or oval, has a diameter equivalent to 10 mm maximum.
According to another embodiment of the invention, the orifice(s) that enable to inject pressurised water into the mixing chamber, comprise a hole leading to the said chamber, whose diameter is approx. 1 mm and whose length is in the same order as the said diameter, whereas the said hole can be provided in the centre of a large diameter bore or countersink, at least ten times the diameter of the said through hole, in order to form a kind of membrane at the inlet of the water jet into the said mixing chamber.
This invention suggests, also in combination with nucleators, a spray head whose capacities can for instance be modified easily according to the requirements.
According to the invention, the spray head, with which the nucleation device is associated, consists of a body which comprises at least two spray nozzles supplied separately with pressurised water, which head comprises a foot that is provided in order to be attached to a post, which post comprises for instance several water supply ducts and possibly pressurised air supply ducts, which ducts are arranged in relation to orifices provided in the said foot in order to supply the various nozzles of the said head.
According to another embodiment of the invention, the body of the spray head consists of a ring-shaped moulded part or other, made of light alloy, which part is fitted with supply chambers for the pressurised water spray nozzles, which chambers are for example obtained directly by a moulding process, whereas each of them is supplied via a duct arranged at the lower portion of the body in order to enable complete drainage of the said chambers when the spray head is inactive, which chambers are moreover adjacent, arranged side by side, offset axially with respect to the axis of the spray jet, and they are each traversed by axial drillings that enable to accommodate the said cartridge-like spray nozzles, which cartridges comprise at least one orifice that leads to one of the chambers, to supply them with pressurised water.
The spray head may thus comprise nozzle sets; each set being supplied by the same chamber.
Still according to the invention, the spray head comprises, upstream of the supply chambers of pressurised water spray nozzles, a chamber supplied with pressurised air, and the cartridge of the nucleation device goes through the various pressurised water chambers and leads at its upstream end to the said pressurised air chamber, which cartridge also contains at least one orifice leading to one of the said pressurised water chambers, and especially the main chamber arranged upstream of the others, to enable injection of water into the air stream that circulates in the said cartridge through the mixing chamber, and this air-water mixture is sprayed by the nozzle of the nucleator in the form of ice or snow.
The spray head with the integrated nucleation device according to a variation of the invention, comprises at least two nozzles supplied separately by distinct pressurised water systems, whereas these nozzles are arranged radially on the periphery of a tubular jacket whose axis is close to the vertical under normal operating conditions, which jacket contains a core that is fitted with radial walls in order to divide, in a watertight manner, the internal space of the said jacket into several chambers:xe2x80x94a main chamber andxe2x80x94at least one secondary chamber that is implemented after the main chamber if necessary, which chambers serve for supplying one or several nozzles, which core is fitted with internal ducts connected to the said pressurised water systems in order to supply each chamber.
Still according to the invention, the upper portion of the spray head comprises a cap fitted with at least one nucleation device provided beside or in the vicinity of the nozzle(s) of the main chamber, which device is supplied with pressurised water and with pressurised air, whereas pressurised water is supplied via the supply duct of the said main chamber, which duct goes through the said cap and whereas air is provided by a specific duct arranged in the core and in the cap, in the centre of the said core and cap.
Still according to the invention, the nucleation device is integrated radially in the head, going through the tubular jacket and is shrink-fitted in the centre core to reach the pressurised air supply duct.
According to a variation, the nucleation device comprises a cartridge making up the mixing chamber and two spray nozzles for the air-water mixture, whereas each nozzle is oriented parallel to the faces of the dihedra in which for instance the pressurised water spray nozzles are aligned.
In the various cases above, the body of the nucleation device is partially immersed in the water circulating in the main chamber, thereby preventing the small orifice(s) from being frozen up or clogged, thanks to permanent circulation of water in the said chamber.
According to another provision of the invention, still with a view to avoiding frost phenomena at the head, the various supply ducts of the chambers of the said head lead to the lower portion of each chamber thereby ensuring complete drainage of the said chambers once the installation has stopped.